U.S. patent application number 09/935336 was filed with the patent office on 2002-02-28 for system for remote diagnosis of the state of wear of the suction and delivery valves of reciprocating compressors.
Invention is credited to Morganti, Piero.
Application Number | 20020023495 09/935336 |
Document ID | / |
Family ID | 11445746 |
Filed Date | 2002-02-28 |
United States Patent
Application |
20020023495 |
Kind Code |
A1 |
Morganti, Piero |
February 28, 2002 |
System for remote diagnosis of the state of wear of the suction and
delivery valves of reciprocating compressors
Abstract
A system for remote diagnosis of the state of wear of the
suction and delivery valves of reciprocating compressors (20),
comprising at least one piezoelectric seismic sensor (12), applied
to each cylinder (14) of the compressor (20), which transforms the
vibrations generated by the noise of the valves into an electric
signal, from which, by means of appropriate amplification and
filtering methods, the envelope of the resulting narrow band signal
is obtained; the signal obtained is then digitised, and transmitted
to a remote diagnostics center (16), in order to be monitored.
Inventors: |
Morganti, Piero; (Prato,
IT) |
Correspondence
Address: |
NIXON & VANDERHYE P.C.
8th Floor
1100 North Glebe Road
Arlington
VA
22201
US
|
Family ID: |
11445746 |
Appl. No.: |
09/935336 |
Filed: |
August 23, 2001 |
Current U.S.
Class: |
73/587 |
Current CPC
Class: |
F04B 51/00 20130101;
F04B 39/10 20130101 |
Class at
Publication: |
73/587 |
International
Class: |
G01D 007/00; G01N
029/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 31, 2000 |
IT |
MI2000A001932 |
Claims
1. System for remote diagnosis of the state of wear of the suction
and delivery valves of reciprocating compressors (20), of the type
based on use of sound emissions which are emitted by the said
valves, when, after they become worn, they recirculate part of the
compressed gas, characterised in that they comprise at least one
sensor device (12), which is positioned on one of the cylinders
(14) of the said reciprocating compressor (20), with which there is
associated an amplifier device (22), which amplifies the signal
input, and transmits it to electronic processing and control means
(24), which, in turn, are connected, by means of at least one
communication line (28), to a remote diagnostic and monitoring
system (16).
2. System according to claim 1, for remote diagnosis of the state
of wear of the suction and delivery valves of reciprocating
compressors (20), characterised in that the said diagnostic and
monitoring system (16) monitors the said sound emissions of the
valves remotely, such as to warn an operator of the need to stop
the said compressor (20), and carry out maintenance on the said
valves.
3. System according to claim 1, for remote diagnosis of the state
of wear of the suction and delivery valves of reciprocating
compressors (20), characterised in that the said sensor device (12)
consists of a piezoelectric seismic sensor, which transforms
vibrations generated by the said sound emissions of the valves into
a high-frequency electric signal, which is transmitted to the said
amplifier device (22), the said seismic sensor being positioned on
an external surface of the head of the said cylinder (14), at the
corresponding valve to be monitored.
4. System according to claim 1, for remote diagnosis of the state
of wear of the suction and delivery valves of reciprocating
compressors (20), characterised in that the said electronic
processing and control means (24) comprise at least one device for
filtering of the signal, an envelope detector, and a digitiser
converter.
5. System according to claim 4, for remote diagnosis of the state
of wear of the suction and delivery valves of reciprocating
compressors (20), characterised in that the said filtering device
operates in the ultrasonic field of the said sound emission of the
valves.
6. System according to claim 4, for remote diagnosis of the state
of wear of the suction and delivery valves of reciprocating
compressors (20), characterised in that the said envelope detector
determines the envelope of the signal input, with a resulting
signal with a pass-band of 30 kHz.
7. System according to claim 1, for remote diagnosis of the state
of wear of the suction and delivery valves of reciprocating
compressors (20), characterised in that the said communication line
(28) comprises at least one modem (26) and one telephone lane (28),
or radio bridge, or satellite, or Internet/Intranet network.
8. System according to claim 6, for diagnosis of the state of wear
of the suction and delivery valves of reciprocating compressors
(20), characterised in that, on the basis of the average value of
the amplitude of the wave form of the said envelope signal
received, minus the mechanical friction peaks, the said remote
diagnostic system (16), supported by an automatic alarm system,
warns of the need to carry out maintenance on one or a plurality of
valves of the said compressor (20), if the emissions of the valves
in the ultrasonic field exceed predetermined amplitude values.
9. System according to claim 1, for diagnosis of the state of wear
of the suction and delivery valves of reciprocating compressors
(20), characterised in that the said sensor devices (12) and the
said amplifier devices (22) are installed on the said cylinder (14)
of the compressor (20), whereas the said electronic processing and
control means (24) are installed on the machine, and are
interconnected to one another and to a data acquisition system.
10. System for remote diagnosis of the state of wear of the suction
and delivery valves of reciprocating compressors (20),
substantially as described and claimed, and for the purposes
specified.
Description
[0001] The present invention relates to a system for diagnosis of
the state of wear of the delivery and suction valves of
reciprocating compressors.
[0002] As is known, the term reciprocating volumetric compressors
is used to indicate the thermal operating machines in which energy
is transmitted by means of compressible fluids, substantially by
varying their specific volume.
[0003] The variations of volume and the corresponding variations of
pressure are obtained by the effect of the decrease of volume of
the operating chamber of the machine, whereas the final variations
are determined by the pressure conditions upstream and downstream
from the operating machine itself.
[0004] In particular, the reciprocating compressors function with
variations of volume of an operating chamber, which are obtained by
straight displacement of a rigid body along the generatrices of a
cylindrical cavity, and can be controlled by means of a crank
mechanism, which permits transformation of motion from continuous
circular, such as that which is generally supplied by electric and
thermal motors, to reciprocating, as required in the specific
case.
[0005] Like other reciprocating machines, for implementation of the
different phases of the work cycle, the compressors of this type
require an appropriate system of distribution, which is implemented
almost exclusively by means of valves of two types: those of which
the opening and closure is controlled, by means of a more or less
complex kinematic chain, by the crankshaft of the compressor
(controlled valves), and valves of the automatic type, which on the
other hand are activated directly by the pressure differences
between the interior and the exterior of the operating chamber.
[0006] At present, most compressors have automatic valves produced
using different solutions, which are substantially derived from
plate or cap valves. Sealing is assured by the contact of various
strips on a plate, which acts as a valve seat, and which contains
numerous slits; the various strips are subjected to the action of
return springs, which facilitate the closure and damp the
opening.
[0007] In all cases, it is necessary to assure that the worn valves
are replaced in time, since malfunctioning of the valves leads to
decreases in the cross-sections of passage, and thus to reduced
flow rates, with consequent unacceptable losses of load, which
change the ideal work cycle into a significantly disadvantageous
real cycle. However, at present, replacement of the valves takes
place after programmed maintenance has been carried out, i.e. when
it is not yet strictly necessary, or after the valves have broken,
resulting in undesirable stoppage of the compressor.
[0008] The disadvantages caused are apparent in both cases; in
fact, these interventions give rise to interruption of production,
whether the machine is stopped even if it is not necessary, or if
the stoppage is unforeseen, owing to sudden breakage of one or more
valves, or if the stoppage is longer than planned, because of any
repairs of further components of the machine damaged by breakage of
the valve(s).
[0009] As previously stated, the state of wear of a valve is
indicated by various parameters, such as a decrease in delivery
pressure, decrease in flow rate, increase in the temperature of the
valve body, and noisiness of the valve in the field of audible
frequencies.
[0010] Thus, by monitoring the undesirable variation of these
parameters at each valve, it is possible to determine a valve which
is malfunctioning, and to intervene mechanically in order to
control the actual state of wear of that valve.
[0011] In all cases, periodic inspections of the state of wear are
involved, which require stoppage of the compressor, with the same
disadvantages as those previously described.
[0012] Alternatively, in order to evaluate the state of the valves
during normal functioning of the compressor, it is known to make
use of the phenomenon according to which the valves emit sound
waves when they recirculate part of the compressed gas, after they
have become worn.
[0013] In fact, the valves of the cylinders, both for suction and
delivery, can undergo breakages of the rings, or they can function
incorrectly owing to the presence of dirt or solid substances
between the rings themselves and the corresponding stop seat.
[0014] In all these cases, there are conditions of reflux of the
gas, which, as it heats up during the compression phase, gives rise
to an increase in the temperature of the valve itself, the
corresponding valve caps, and the body of the cylinder.
[0015] The progressive and physiological deterioration of the
sealing surfaces, which come into contact between the valve and its
seat, generate a phenomenon of recirculation of the gas, between
the high-pressure side is and the low-pressure side of the
compressor, as a result of the irregularities which form on these
surfaces over a period of time.
[0016] The recirculation of gas is caused by numerous small jets of
gas, which escape through the irregularities of the contact
surfaces, and give rise to emission of sound or ultrasound;
measurement of this emission therefore provides an index of
evaluation concerning the state of wear of the surfaces.
[0017] The object of the present invention is thus to indicate a
system for diagnosis of the state of wear of the suction and
delivery valves of reciprocating compressors, which makes it
possible to monitor remotely the sound emissions produced by the
malfunctioning valves, such as to be able to warn the operator
during use, of the real need to stop the machine for maintenance on
the valves.
[0018] This object and others according to the invention are
achieved by a system for remote diagnosis of the state of wear of
the suction and delivery valves of reciprocating compressors,
according to claim 1.
[0019] According to preferred, but non-limiting embodiments of the
invention, in addition, the system for diagnosis uses a
piezoelectric seismic sensor applied to each cylinder of the
compressor at the valve to be monitored, which transforms the
vibrations generated by the noise of the valves into a
high-frequency electric signal, to be transmitted to a
signal-amplifier device.
[0020] In addition, the electronic processing and control means
comprise a signal-filtering device, which operates in the
ultrasonic field of sound emission of the valves, an envelope
detector, which determines the envelope of the input signal, with a
resulting signal with a pass-band of 30 kHz, and a multiplexer for
transmission of the data on a communication channel, such as a
telephone line, a radio bridge, or satellite, or Internet/Intranet
network. Advantageously, the system for diagnosis of the state of
wear of the suction and delivery valves of reciprocating
compressors according to the present invention, makes it possible
to monitor remotely, from a remote seat, the sound emission
produced by the valves in conditions of malfunctioning and imminent
breakage of the latter, such as to warn the operator at the machine
of the real need to stop the machine for maintenance or complete
replacement of the valves.
[0021] By this means, it is no longer necessary for the operator to
undertake periodic or planned stoppages of the compressor, or
emergency interventions in order to repair any breakages of the
valves; on the contrary, in the case of abnormalities of a valve,
it is possible to detect and locate the occurrence of the
degenerative phenomenon in good time.
[0022] In addition, the system for diagnosis which is the subject
of the invention makes it possible to inform the operator of the
machine accurately of the particular cylinder of the compressor
which requires intervention, for maintenance on the valves.
[0023] Taking into consideration the fact that a reciprocating
compressor may contain up to 12 cylinders with radial or axial
valves, this possibility is extremely advantageous, since it
prevents an entire series of dismantling operations, which would
prove to be unnecessary once the malfunctioning valve(s) had been
located.
[0024] Finally, the evaluation of the increase in noise over a
period of time is an indication of the residual life of the valve,
and makes it possible to stop the machine, for replacement of the
valve, only when it is actually necessary.
[0025] The characteristics and advantages of the system according
to the present invention, for diagnosis of the state of wear of the
suction and delivery valves of reciprocating compressors, will
become more apparent from the following description of a typical
embodiment, provided by way of non-limiting example, with reference
to the attached schematic drawings, in which:
[0026] FIG. 1 represents a block diagram of the system according to
the present invention, for remote diagnosis of the state of wear of
the suction and delivery valves of reciprocating compressors, in
which cylinders with radial valves are schematised generically; in
this respect, it should be noted that the present invention can
also be applied to cylinders of reciprocal compressors which have
axial valves;
[0027] FIG. 2 is a cartesian graph, which represents the envelope
of a signal obtained from a sensor applied to a cylinder of the
reciprocating compressor according to FIG. 1, in conditions of
considerable wear of the valve; and
[0028] FIG. 3 is a Cartesian graph, which represents the envelope
of a signal obtained from a sensor applied to a cylinder of the
reciprocating compressor according to FIG. 1, in conditions of
negligible wear of the valve. With reference to the aforementioned
figures, 14 indicates schematically a cylinder, which can be
respectively of the type with radial valves or axial valves, of a
reciprocating compressor 20, and 12 indicates piezoelectric
sensors, each of which is positioned on the vertical outer surface
10 of the head of the cylinder 14, close to the corresponding
suction or delivery valve.
[0029] 22 indicates amplifier devices, each of which is connected
closely and locally to the corresponding piezoelectric sensor 12,
whereas 24 indicates a block for measurement of the signals output
by the amplifiers 22, comprising a multiplexer, an envelope
measurer, and an electronic data acquisition system; these devices
are usually installed in a suitable control area provided in the
vicinity of the compressor 20.
[0030] Within the same area, there is also installed a modem 26,
the input of which receives the signal output by the block 24.
[0031] The signal processed by the modem 26 is then transmitted on
a telephone line 28, in order to be transmitted to a remote
diagnostics centre 16.
[0032] Each piezoelectric seismic sensor 12 applied to each
cylinder 14 of the reciprocating compressor 20 transforms the
vibrations generated by the noise of the valves, in conditions of
malfunctioning of the latter, into an electric signal, with
frequencies which can be as much as 1000 kHz.
[0033] After amplification of the signal, which is obtained by
means of the local amplifier 22, connected to each sensor 12, the
same signal is filtered in a frequency band of 700-1000 kHz
(ultrasonic field of noise of the valve), and the envelope is
determined in the block 24 with a resulting signal, with a
pass-band of 30 kHz.
[0034] The multiplexer in the block 24 permits digitisation of the
signal, and thus, the latter is transmitted, via the modem 26 or
another appropriate transmission means (radio bridge, satellite,
Internet/Intranet network or the like), to a corresponding remote
diagnostics centre 16. On the basis of the amplitude of the wave
form of the signal of the envelope received, an operator of the
remote diagnostics centre 16, supported by an automatic alarm
system, of a known type, can warn the operator of the compressor 20
of the need to carry out maintenance on one or a plurality of
valves, when the noise in the ultrasonic field exceeds
predetermined amplitude values.
[0035] By this means, the remote diagnostics centre 16 prevents the
machine operators from having to establish exactly is the times for
periodic checks of the valves, or from having to carry out
emergency repairs as a result of sudden breakages of the
valves.
[0036] FIGS. 2 and 3 indicate respectively the envelopes of two
signals obtained from a piezoelectric seismic sensor 12, applied to
a cylinder 14 of a reciprocating compressor 20.
[0037] In particular, the graph in FIG. 2 represents an envelope of
a signal obtained from a sensor 12 applied to a cylinder 14, in
which there is no appreciable wear of the valve; in fact, the
average value in Volts, in the time t, of the amplitude of signal
V, minus the peaks, which are caused purely by phenomena of
mechanical friction, is very low.
[0038] On the other hand, the Cartesian graph in FIG. 3 denotes
strong wear, which requires maintenance of the valve, since the
average signal value V in the time t is extremely high.
[0039] In practice, on the basis of the wave form of the signals
received, the remote diagnostic centre 16 transmits a communication
remotely to the machine operator, thus managing maintenance of the
valves in the times required, and at the correct moment.
[0040] This communication is carried out on the basis of display of
the signals on a series of monitors of the remote monitoring centre
16; the monitors carry out the functions of display of the signals
measured by all the piezoelectric seismic sensors, or of the
maximum signal measured (as an average value), of alarm and
stoppage, and of supply of the sensors on the machine.
[0041] The signals which are obtained from the valves with the same
effect, and which carry out the same function, are compared
continuously on the monitors of the diagnostics centre 16, which
generates an alarm if one of the signals detected diverges from the
average value of the signals normally considered.
[0042] By this means, malfunctioning of one valve, compared with
the other suction or pressure valves for other effects of the
cylinders 14 which have the same compression phase, is brought
immediately to the attention of the machine operator.
[0043] The description provided makes apparent the characteristics
and advantages of the system according to the present invention,
for remote diagnosis of the state of wear of the suction and
delivery valves of reciprocating compressors.
[0044] In particular, these are represented by the following:
[0045] remote monitoring of the noise produced by the valves of the
reciprocating compressors, so as to warn the machine operator of
the real need to stop the machine for maintenance;
[0046] programmed periodic stoppages of the machine, or emergency
interventions to repair any breakages of the valves, are not
necessary; and
[0047] accurate information concerning the cylinder on is which
action must be taken in order to carry out maintenance on the
valves, thus avoiding unnecessary dismantling.
[0048] Finally, it is apparent that many other variations can be
made to the system which is the subject of the present invention,
for remote diagnosis of the state of wear of the suction and
delivery valves of reciprocating compressors, without departing
from the principles of novelty which are inherent in the inventive
concept.
[0049] It is apparent that, in the practical embodiment of the
invention, any materials, dimensions and forms can be used
according to requirements, and can be replaced by others which are
technically equivalent.
[0050] The scope of the present invention is defined by the
attached claims.
* * * * *